Satellite data has shed new light on seismic hazard in one of the world’s most deadly earthquake zones.

Published today in Nature Communications, the study describes how tectonic strain builds up along Turkey’s North Anatolian Fault at a remarkably steady rate.

This means that present-day measurements can not only reflect past and future strain accumulation, but also provide vital information on events still to come.

The strain, which builds up as Turkey is squeezed between three major tectonic plates, has caused almost the entire length of the fault to rupture since 1939 in a series of major earthquakes gradually migrating east to west towards Istanbul.

Led by Ekbal Hussain, the team used satellite images from the European Space Agency’s Envisat mission to identify tiny ground movements at earthquake locations along the fault.

Dr Hussain explained: “Because we know so much about the fault’s recent history, we could look at the strain build up at specific places knowing how much time had passed since the last earthquake.”

The 600-plus satellite images, taken between 2002 and 2010, provided insights into the equivalent of 250 years of the fault’s earthquake repeat cycle.

Remarkably, apart from the ten years immediately after an earthquake, strain rates levelled out at about 0.5 microstrain per year, equivalent to 50mm over a 100km region, regardless of where or when the last earthquake took place.

Dr Hussain added: “This means that the strain rates we measure over the short term can also reflect what’s happening in the longer term, telling us how much energy is being stored on the fault that could eventually be released in an earthquake.”

Until the satellite era, it was difficult to get a clear picture of how strain built up on the fault. Now, satellites like Envisat, alongside the newer Sentinel-1 mission, can detect ground movements of less than a millimetre, indicating how and where strain is accumulating.

The findings suggest that some existing hazard assessment models, which presume that strain rates vary over time, need to be rethought. This is especially true for regions where there are long gaps between earthquakes, such as the Himalayas.

Co-author Professor Tim Wright said: “Discovering this consistent strain accumulation will help us to reassess how we model seismic hazards, as well as improving understanding of the earthquake cycle worldwide.”

[1] The full paper is: Hussain et al. (2018) Constant strain accumulation rate between major earthquakes on the North Anatolian Fault, Nature Communications
[2] Lead author Ekbal Hussain is now a Remote Sensing Geoscientist at the British Geological Survey

Working professionally as a remote sensing scientist it is perhaps no surprise that I’m lover of maps and data. And so I was very excited to read New Views, a beautiful book full of fascinating maps and cartographic visualisations depicting global data in all its visual glory.

Created by Alastair Bonnett, Professor of Social Geography at Newcastle University, it is worth noting that many of the maps and/or the data behind them are the creation of other scientists and organisations, including NASA and various bodies of the United Nations. In each case Alastair declares the source of the data, often with a quote or two from the original creators as well as some fascinating insights gleamed from the visualisations.

The book broadly cover three main topics: Land, Air and Sea, Humans and Animals, and Globalisation. The fifty maps are illustrated with highly visual and extremely informative data, which gives a global perspective to events like asteroid strikes, fire activity, religious diversity and critically endangered languages. My favourite was the global energy flux, which depicts the abundant energy infrastructure of the power hungry West with the growing energy fluxes in the booming countries of East Asia; while the dark expanses of the African continent illustrate the energy access and development challenges of the region.

So this book isn’t purely a collection of maps, it is a vivid illustration of global wealth inequality, of health disparities, of economic development, and environmental treasures. The global perspective they offer show us that we live in a highly diverse and unequal world, and only through such visualisations can we appreciate the global nature of our influence and our impact on the world.

The book ends with a mention, that delighted the map nerd in me, of the various map projections used in the book. It would have been great to learn why the author chose to use certain projections in his visualisations but alas, we shall never know!

‘Give me an atlas over a guidebook any day, for there is no more poetic book in the world.’ – Judith Schalansky

Like this:

Half awake, half asleep. The room is shaking. You realise you are not at home. You are in central Italy. Now the room is really shaking, you sprint over to hide under the desk as the floor moves under your feet, grabbing clothes as you go. The shaking continues, you put on the random assortment of clothes, pulling the bag you packed the night before, with the essentials to survive, close to you, wondering when the shaking will stop. Preparing mentally to be buried under the roof and hunker under the desk until the rescue team gets to you, you listen as the doors and windows rattle and bang. Then there is silence.

People gathered in Ascoli Piceno town square, not long after the earthquake. Copyright: Huw Goodall

Pulling your shoes on (why didn’t you untie them last night!) you run into the corridor, your colleagues are out there, everyone is unhurt. Down the gloomy hotel corridor you all hurry out into the square, where slowly but surely the population of Ascoli Piceno gathers in the beautiful early morning sun. After an hour or so delay, including dashing back into the ancient building to grab field kit, interviews with the BBC and a delayed breakfast, you escape from the medieval town towards the epicentre of the earthquake.

Dodging boulders on the drive up towards the epicenter. Copyright: Huw Goodall

Driving up the winding mountain roads, dodging between boulders that have been dislodged by the shaking, your team of 4 make their way towards the centre of the earthquake. As you approach, the tiny villages that dot the route show increasing signs of damage. Then you see it. The rupture. This is where the earth has been cut by the quake. The work begins. High precision surveys are taken from this site, after a brief discussion it is decided to return to where you were working the previous day and see if the fault has moved in the earthquake there too.

Our first encounter with the fault rupture, south of Mt Vettore. Copyright: Huw Goodall

This involves driving through the isolated town of Castellucio, a stunning hilltop village, famous for its lentils. As you drive up the hill, the residents are in the street. Your Italian is only good enough to order food, but you can tell they are scared, confused and don’t know why you are there. You are probably the second car at most that has passed this way since the earthquake that morning. The destruction is clear, walls collapsed a pancaked building along the road, other houses simply gone. There is a helicopter landing in the street. People are everywhere.

Before and after images of the destruction at Castelluccio.

Eventually the situation is explained in a hash of Italian and English and you are allowed to pass through, to continue to do your work as the people of the village continue to take stock. The next two weeks are non-stop field work, police checkpoints, late dinners and early starts. You measure how the fault has ruptured the surface, using a high-tech laser scanner, GPS, cameras and the good old fashioned ruler and notebook.

The fault on Mt Vettore, the bad of pale rocks (red line) shows the amount of movement of the ground during the earthquake I experienced. Copyright: Huw Goodall

We spent the fortnight mapping new parts of the rupture as well as repeating measurements at some sites, to generate a picture of how the fault is moving in the days after the earthquake. This data set will be unlike any other in existence and hopefully will give us an insight into why earthquakes happen the way they do.

Huw is a PhD student in the School of Earth and Environment at the University of Leeds. His work involves using precise chemical analysis of earthquake faults to understand how they have moved in the past.

Like this:

Incredible footage of lava flows out of Erta Ale volcano in northeastern Ethiopia. Erta Ale is located in the Afar depression, a badland desert area that is part of the northern section of the East African Rift system. The volcano is one of only a few in the world with a constantly active lava lake.

Like this:

Bangladesh is one of the most disaster-prone countries in the world. In addition to frequent cyclones and drought, large areas of the country are at risk of earthquakes.
With densely populated cities, even a relatively small earthquake could have catastrophic consequences. Amrai Pari (Together We Can Do It) is harnessing the power of animation to help people be better prepared. Find out more about the project: http://bbc.in/2gsG8Tx

Like this:

Hurricanes are one of the planet’s most destructive natural weather phenomenons. Firstly, for those living in hurricane prone regions, it is important that communities follow and adhere to local emergency services and action plans.

Hurricane Genesis

Hurricanes are very large storm whose birth originates in the tropical oceans. They rotate about a central axis commonly called ‘the eye’. The oceans are a massive source of heat energy. Variations in sea surface temperature result in pressure differences in the atmosphere which cause storms to build up.

Tropical storms are characterised by their geographic origins. Image: NASA

To be classified as a hurricane a storm must reach wind speeds of at least 74 miles per hour. The rotation of the Earth gives these storm their characteristic spiral shape. Cyclonic storms in the northern hemisphere rotate anticlockwise while those in the southern hemisphere rotate clockwise.

Hazards

The main hazards from hurricanes are strong winds (up to 150 miles per hour for the very large storms) and high volumes of rain. Hurricane winds can uproot trees and destroy houses. Large amounts of rainfall in a short period of time can cause floods and rising groundwater tables.

The water-clogged landscape remains unstable, with increased risk of landslides and surface failures, for many years after a particularly large event. For example, there were increased number of landslides in Taiwan for 6 years after Cyclone Bhola.

The effect hurricanes have on people’s lives is illustrated by the word hurricane itself; after the Caribbean god of evil, Hurrican. They are a devastating force of nature.

Cyclone Bhola (1970) is historically the worst event for deaths with reported numbers as high as 500,000 people dead, mostly in Bangladesh.

Hurricane Katrina, which struck the east coast of the U.S. in 2005 is the most costliest hurricane with overall damage exceeding $100 billion.

The 1979 Cyclone Tip was the most intense hurricane ever recorded with wind speeds around 190 miles per hour. It was also the largest hurricane with a diameter around 2,170 kilometres.

Hurricane Sandy (U.S. east coast, 2010) was an abnormally large event due to the fusion of a tropical hurricane and a winter storm. With rising temperatures due to global warming these hybrid-storms are expected to become more frequent.

What can we do?

Cyclone Mahasen hit Sri Lanka, Bangladesh and Burma last season in May and resulted in far less deaths than expected thanks to swift action from the local governments. This shows that rapid response can save lives.

Proper preparation and sufficient warning can save thousands of lives every year.

Houses with appropriate shelters (as in the U.S.) need to be built in hurricane prone regions. Proper training should be given from early school level onwards on the appropriate actions to take before and after such events: e.g. having enough clean drinking water, tinned food, spare batteries for lights, mobile phone chargers, first aid kits etc.

Have a rapid response system in place from the national governmental level to manage pre-event evacuation (if needed) and post disaster recovery.

There is no clear agreement on what sort of effects climate change and global warming will have on hurricanes. However most scientists agree that the change will be for the worse whether it is in the form of increased number of hurricanes each year, increased size of the hurricanes or changes to the length of the hurricane season . We need to invest more into understanding the science behind these storms and the effects global warming will have on their magnitude and frequency of occurrence.